1. Field of the Invention
The present invention pertains to cooking appliances and, more particularly, to a telescoping downdraft ventilator with the ability to fit behind an appliance such as a built in oven placed below a cook top.
2. Discussion of the Related Art
Telescoping downdraft ventilators of present designs are long rectangular boxes having a construction of an inner and outer box of single walled or a double walled with insulating air in between the telescoping and base housing. There is also a telescoping rectangular box of some sort to open up the interior of the box for exhausting. Typically, there is about 1¾ inches in depth shown at the top when the ventilator cap is closed. Standard widths range from 27 inches to 48 inches. The top trim of the telescoping rectangular box is fixed in a horizontal plane and is found flush with the counter. The centrifugal type fan/blower, attached to the base housing, has been by a single blower, attached on the side with airflow at 90 degrees from the side of the base box. The overall size of an attached fan/blower ranges from six to twenty-three inches, the components of which, e.g., a fan/blower, motors, mechanical components and sheet metal, is installed under a cabinet. The typical blower has been designed to draw air down with the use of a centrifugal-type fan/blower. The blower removes contaminated air from a cook top surface, removes the interior air of the box and either exhausts it outside or returns it to the room. A centrifugal fan creates higher pressures than an axial flow fan. In present designs, the airflow stream must move across the work area, being pulled from the front of the work area to the back where the ventilator is located. The air must travel through a ninety degree turn once inside the chamber and move downward. The air stream must take another 90 degree turn into an opening with a smaller diameter than the ventilator chamber. At this point, the air stream has entered the blower and a centrifugal fan/blower redirects the air downward for exhausting. With the numerous bends and turns the air stream must take, a large amounts of draw (i.e., vacuum, or suction) is needed to overcome these losses. The large draw requires a large motor which increases costs, noise, size and weight.
With the new trend of having a drop-in cook top surface on a counter with a built-in wall oven placed below the cook top in a standard cabinet, the space behind the cabinet is limited to less than one inch of space or less. A typical telescoping down draft ventilation system is about six inches in depth and therefore cannot fit it in the back of a cook top while providing enough space for the oven. Further, present ventilation systems on the market go through long runs of ducting in order to have a fan/blower located remotely. By not having the fan/blower part of the telescopic down draft, issues such as drawing air into the system, wiring, user control and installation problems may arise.
Present designs typically incorporate a centrifugal fan or blower, consisting of a wheel with blades on the circumference and a shroud to direct and control the airflow into the center of the wheel and out at the periphery. Motors are mounted on the outlet side of the fan/blower housing. This is done because of cost and to keep them out of the stream of contaminated air. The blades move the air by centrifugal force, literally throwing the air out of the wheel at the periphery, thereby creating a vacuum/suction inside the wheel. Basic design types of wheel blades in centrifugal blowers include the forward curved and backward inclined blades.
Forward curved wheels are operated at relatively low speeds and are used to deliver large air volumes against relatively low static pressures. The inherently light construction of the forward curved blade does not permit the wheel to be operated at speeds needed to generate high static pressures and therefore cannot be used in telescoping downdraft ventilators.
The backward inclined blower wheel design has blades that are slanted away from the direction of the wheel travel. The performance of this wheel, specifically a high efficiency, high cubic feet per minute (cfm) and rugged construction makes it suitable for high static pressure applications. The maximum static efficiency for this type of blower wheel is approximately 75 to 80%. A drawback is that it must be designed for twice the speed, which increases the cost of the unit.
Axial flow fans are also not used for present telescoping downdraft ventilators. This is due to the belief that this type of fan cannot provide the static pressure needed for drawing, its size and spacing requirements. Axial flow fans come in three basic types. The propeller fan (i.e., the house hold fan), the tube axial fan and vane axial fan (cross flow or tangential). The first of these is the most familiar. The propeller fan consists of a propeller blade and associated aperture that restricts blow back from the sides. Without the aperture, the fan is not truly a propeller fan, since it cannot positively move air from one space to another. The aperture is usually sheet metal/plastic designed to fit closely around the periphery of the propeller. The tube axial fan (typically found in computers) is literally a propeller fan in a tube. In this case the tube replaces the aperture. The tube axial fan is an extension of the propeller fan with increased flow quantity, pressure and efficiency, due to the reduced air leakage at the blade tips. The vane axial fan (cross flow or tangential) is a tube axial fan with the addition of vanes within the tube to straighten the airflow. The air flow changes from helical flow imparted by the propeller into a nearly straight line flow. In the process, the vane axial fan increases the pressure and efficiency of the air flow while reducing the noise.
In general the propeller fan operates at the lowest pressure of the three types. The tube axial fan is somewhat higher with the vane axial fan supplying the highest-pressure output of the three. Vane axial fans are noted for use when available space for installation is limited, such as in computers. In down draft ventilation technology, this method of moving air has never been used.
Static efficiencies of 70 to 75% are achieved with vane axial fans. The cfms and static performance range of the vane axial fan is similar to that of a centrifugal. Horsepower requirements are about the same for both designs.
With all present telescoping downdraft ventilators using a centrifugal type fan/blower, airflow is drawn in at a 90 degrees turn to the fan through a small opening and then another 90 degree bend at the cook top surface. The fan/blower is typically located under the counter in the cabinet. The bending of the airflow reduces the suction effectiveness of a telescoping downdraft ventilator using a centrifugal fan/blower. Because of the air stream bending, a large loss of suction occurs, resulting in poor ventilation performance. The best ventilators on the market only capture about 60% of the steam coming off a four-burner cook top. Typically, 100% of steam from the back two burners is captured while only 10% of the steam is captured from the front two burners. Also, a big issue with these centrifugal fan/blower is their noise during operation. These units are very loud and tends to be a problem with present telescoping downdraft ventilators.
Typical telescoping downdraft ventilators only stop at a full-up, or open, position and a full-down, or closed position. Present telescoping downdraft ventilators use mechanical or tactile-type controls to control and operate both the removal of air and the up and down stop points. These mechanical/tactile type controls may be inaccurate and have a tendency to not to work properly. Present designs use knobs and slides to set and control mechanical switches for setting the desired fan/blower speed and stops. These types of products provide an increased rate of failure and other operating problems. The mechanical switches used are inaccurate in their setting and repeatability. These present controls have problems maintaining a set point with swings in repeatedly reaching set points. This is partly due to the design of the telescoping downdraft ventilator and method of drawing air, but also because of the inaccuracy of the mechanical switches themselves. Mechanical control switches have known issues such as hysteresis, which contributes to their inaccuracy in hitting a set point or repeating a function. This can be evidenced by turning the control switch to the right and stop at a set point or turning the same mechanical switch going past the set point and then turning the control to the left stopping at the set point. Both actions end with the same set point selected but the resulting speed will be different. Mechanical levers are used and over time they change positions causing additional problems for the user.
Mechanical switches used in present telescoping downdraft ventilators are subjected to the effects of surrounding environment including heated air, steam, oils, greases, particulates and effluents. Without proper protection these switches cause problems and eventually fail completely. If subjected to cold temperatures, mechanical switches may work slowly, crack, become hard to turn, fail to operate, lubrication can harden causing the operation not to function, cause switch chatter resulting in premature failure or reduced life of product, and cause other user issues. If subjected to hot temperatures, mechanical switches may operate slowly from the lubrication drying out, crack, discolor, become hard to turn, fail to operate, cause switch chatter, cause premature failure or cause user issues when trying to set or operate these controls. If mechanical switches and/or controls are subject to outdoor environments like rain, snow, sun, UV, special sealings are required to prevent intrusion of these environmental conditions that cause premature failure or reduced product life. Special sealed controls used in these environments increases the price of a telescoping downdraft ventilator, mechanical switches and controls when used outdoors in telescoping downdraft ventilator of present design need to be covered, protecting them from the environment. This protection increases the cost for these products and may introduce safety issues.
Present design telescoping downdraft ventilators may use linear tactile electronic control pads, are using tactile type switches with some type of membrane pad over these pads for controlling the functions. The use of tactile switches causes the manufacturer to have to add extensions to these in order to stick out so the user can operate the unit. This addition causes the user to press hard in order to use the rubber or other plastic like material button. This also sets up an area for contamination to get in which can cause problems or failure. In the manufacturing process of these tactile switches, contamination can enter the space, which over time causes problems for the user and sometimes results in failure. In an environment having grease, heat, odor, particulates, and other fluids may cause any type of gap to be filled with contamination. Thus adding an extension to any switch can cause problems for the user both in a build up of contamination but also in the ability to clean. Signs of contamination of build up can be seen around this extension.
No sensors are used to detect the presents of temperature, etc. with these types of telescoping downdraft ventilators. No method of proper airflow detection is provided to the user to indicate the need to change the filter. In fact, the filters on some designs are hidden from view. Other manufacturers have placed a run time and timing out setting as to when the filters should be removed, but this is not or can in fact detect if filters are truly plugged. It is unknown what time it would take for an average use of the filter before it needs replacing or cleaning. For the heavy user the filter would need cleaning sooner and this feature is a problem. For the limited user cleaning is down more often than needed. This is acceptable if the user is using a metal mesh filter that can be washed and replaced, but if the user is using a carbon filter this can get costly.
With present designs, they are limited to islands only, primarily due to their bulky size and lack of room for other appliance below the cook top. With the present units built into an island the ability to provide light is also problem for the user. The present range hood type units are the only ones that provide lighting from above, and a telescoping downdraft ventilator does not provide lighting. Thus the user may have problems using these ventilators because of the lack of lighting. In an island counter installation, the lack of ability to place lights above may exacerbate this problem.
Other issues are presented by present telescoping downdraft ventilators, stemming from the height that these units extend up from the counter top. Some units extend up only 7 inches, where others extend up 15 inches with no adjustability for height. The low extending units provide no effective draw when a large tall pot is place on a burner. They also can blow out the flame on gas burners. On the other hand units that extend 15 inches up provide limited effectiveness when using a frying pan. On some of the taller fixed height units, large filters are used. It has been reported that the drawing air can blow out the gas flame. On ranges with auto sparking for relighting of the gas burners, it has been reported that these ventilators cause continued sparking due in part to the ventilator blowing out the flame. No present ventilators provide varying heights, which would reduce the problems seen by these other units. On the other hand when installing a cook top and wall oven under the cook top the space height can be limited to 8 inches or less. So to have a one-piece telescoping inner member that can rise up to 15 inches is not possible unless you limit the height to less than 7 inches. Again, this is a problem with tall pans with present units.
Quality issues remain with the present telescoping downdraft ventilator operations in their ability to move up and down. Some use a scissor mechanism with many parts, which may jam up, bind, or fail to operate. Also, the operation of these scissors types, are not smooth in movement when moving up or down. They jerk up and down, more like a stepping up or down with stopping in between movements. The use of mechanical switches to detect stopping points for both up and down are used with reliability problems plaguing these units due to the problems associated with mechanical switches and levers. The use of a screw drive unit has been used on high end (i.e., costly telescoping downdraft ventilators) but again they use mechanical switches and levers to detect stopping points for up and down travel and/or elaborate mechanical mechanisms with switches and levers to detect obstructions during travel. These complicated methods may cause additional issues, problems and failure points with costly repair and manufacturing prices.
Present designs are typically for built-in installations on an island counter. Present design are large and bulky. Telescoping downdraft ventilators built into a cabinet on an island counter top and the space below the unit are not available due to the centrifugal blower below and the size of the base housings presently used filling the space. This size limits the telescoping downdraft ventilator from being placed in other areas. This also limits the telescoping downdraft ventilator from being used as a freestanding unit, as a mobile unit, used in a cabinet (e.g., suspended), or in areas that do not have the ability to support a large structural frame. Because of the method of lifting the venting unit cannot be turned upside-down and placed into a cabinet above and have the unit extend down from the back.
Therefore there exists a need for a state of the art telescoping downdraft ventilator in which accurate controlled speed, venting, and removal of contaminates is accomplished in a low, i.e., small, depth installation. There exists the need for an accurate method of controlling the operations and settings. There exists a need for controls to be less susceptible to the environment. There exists a need for the user to be able to view/see the operations, speeds, set points functions, and view the contents on the cook top. There exists a need for a remote control and the controls not using tactile switches. There is a further need to accurately apply and control the height. There also is needed for a new design such that it can be used in other limited spaces and places. There also is needed for the unit to be place in a cabinet above and having the ability to extend down at the back wall or in a cabinet in an island.